MOTOR QUICK DISCONNECTS

[tvlachos]

A CUSTOMER HAS REQUESTED THAT WE INSTALL QUICK DISCONNECTS AT THE MOTORS FOR THEIR SYSTEMS. THESE MOTORS ARE FROM 1 TO 50 HP. THE REASON THEY WANT THESE DISCONNECTS IS TO BE ABLE TO CHANGE OUT A BAD MOTOR QUICKLY AND WITHOUT THE NEED OF A QUALIFIED ELECTRICIAN. THESE QUICK DISCONNECTS ARE BEING MOUNTED ON THE "^$*#@HEADS" OF THE MOTOR AND LEAD BACK TO A REGULAR MOTOR DISCONNECT. I DO NOT BELIEVE THESE QUICK DISCONNECTS ARE SAFE SINCE THEY CAN BE OPENED UNDER LOAD. CAN ANYONE HELP

Removed offensive slang. Charlie

[ April 01, 2004, 07:56 AM: Message edited by: charlie ]

 

[don_resqcapt19]

Re: MOTOR QUICK DISCONNECTS

At least one brand of these devices are suitable for that applicaiton. They are tested to be opened under load. Can you tell us exactally what device is being used in your case?
Don

[ April 01, 2004, 08:46 AM: Message edited by: don_resqcapt19 ]

 

[tvlachos]

Re: MOTOR QUICK DISCONNECTS

WE ARE CURRENTLY USING 6 PIN "CONTACT" QUICK DISCONNECTS FOR OUR THREE PHASE MOTORS. WE HAVE USED HARTING IN THE PAST. ONE POINT THAT I NEED TO MAKE IS THAT THE THE FEMALE END OF THESE QUICK DISCONNECTS CAN BE LIVE ONCE THE QUICK DISCONNECTS HAVE BEEN SEPARATED. THE ARC CREATED WHEN SEPARATING UNDER LOAD IS A CONCERN BUT THE LIVE 460 VOLTS AT THE FEMALE END IS OF GREATER CONCERN. IT CAN BE LAYING ON THE FLOOR IN WHATEVER MAY BE PRESENT WITH 460 VAC PRESENT....YOUR THOUGHTS ON THIS DON ???

 

[don_resqcapt19]

Re: MOTOR QUICK DISCONNECTS

tvlachos,
First, please turn off the CAPs.
I wonder why the 480 would be hot if you are using a 6 pin plug and receptacle? The ones that I have worked on always used the 5th and 6th pins as an intlock that would drop out the starter when the cord is disconnected. As far as unplugging under load, you would have to check the data for the exact item that you are using to make use that it is suitable for load break use. As with all electrical equipment, some common sense is required and the cord should not be left laying around.
I think that we will see a lot more of these types of installations in the interest of safety. It provides a local disconnect in compliance with 430.102(B) and provides a local lock out point for OSHA lock out/tag out.
Don

 

[plugman]

Re: MOTOR QUICK DISCONNECTS

tvlachos,

I am very familiar with the brand of plugs and receptacles that Don referenced in his first post. They do carry a UL rating for disconnecting under load, just like a normal disconnect switch. When disconnected, the receptacles all have a dead front. You would have to try very hard to make contact with the energized parts.

The arc generated when separating is not an issue unless you are disconnecting under a short circuit or are in a hazardous location. The devices have integrated arc chambers that keep the arc contained.

Don's comment about using common sense will keep you out of a lot of trouble.

Most of the horsepower rated devices have only 5 contacts (3 phase, neutral, and ground), but are available with up to 4 pilot contacts rated at 1.5 amps @ 480V.